"The 20-6576 cars are not for a Dreyfuss Hudson 20th Century Set."
These cars appear to be the 1948 paint scheme - essentially, the "diesel" version of the Century scheme, when the grays were reversed: original light body/dark stripe became dark body/light stripe. The MTH catalogue art does not show the lightness of the stripe very well, but I assume that it is there.
These 20-6576 cars need some E7/E8/PA-1 locomotives. The Century Hudsons had lost/were losing their streamlining in this era. Also, the early Century diesel locos had a steam-like light body/dark stripe scheme for a while, for use with the older passenger car scheme, before they were re-painted.
Or something like that.
